Computers

Welding stainless steel

Spot welders are used in the fabrication of automobiles, PC cases, power supplies, microwave ovens, electrical junction boxes, Faraday cages, and various electronics. A spot welder is used because it produces a highly defined point of contact weld. The materials are welded without excessive heating, so working pieces are handled easily. The weld is also highly controlled and repeatable. In this how-to we cover the basics of a spot welder, and then show you how to build one from a microwave oven transformer.

A spot welder’s electrodes serve at least three functions. They transfer electrical energy to the material while also holding it together; this also controls resistance. The greater the pinch force the less the resistance, which results in decreased resistive heating. A lesser pinch force results in increased resistive heating. The electrodes also conduct heat away from the material, while in the off cycles, helping to cool and temper the weld. A resistive spot weld is commonly referred to as a ‘nugget’. Spot welders are generally confined to ferrous materials which somewhat limits their application range. Most produce a weld with low voltage and high current. The welder in this How-to operates from a secondary of 3vac. The primary is 120vac line voltage that should be treated with respect. The low voltage secondary makes the welder very safe, so the electrical shock hazard from the electrode is virtually non-existent. There is however the risk of burn due to the high temperatures as with any welder.

This particular welder is not intended to weld a body panel on your 1966 Jeep; it will not work well on material heavier than 20gauge sheet metal. The intended use is for small projects, for it is not capable of continuous operation. Possible uses are as follows: Welding electrode material for electrolysis cells. Working with the fine components of a vacuum tube. Building a light weight frame for a small robotic platform. Most of us have enough parts laying around to build a spot welder. If you have a microwave oven transformer (MOT) laying around, then you are half way there. On a related note, we had covered a microwave oven arc welder in 2006.

Materials needed

We also needed some heavy gauge copper wire. We used about four feet of 4AWG wire to build the spot welder in the photo. Other materials included scrap 2×6, 2×2, two copper screw type lugs, two copper welding cable lugs, two MIG welder tips, two 4″ x 3/4″ zinc plated corner braces, drywall screws, and three washers.

MOT

Pictured above is a working MOT. The first thing we had to do was remove the secondary coils. Namely the high voltage winding, and the low voltage winding. We used an angle grinder with cut off wheel while being careful not to cut the primary winding.

Removing secondary

We cut the secondary flush with the MOT laminate core. Both sides of the MOT should be cut. Inspect the MOT for signs that the laminate has been welded. We have found that welded MOTs can handle a little more abuse than their sealed only counter parts. If possible try to keep the core insulation intact, where the secondary will be wound. Though it is not a show stopper if the insulation becomes damaged. The insulation makes it a little easier to wrap the heavy gauge secondary.

Removed secondary

After removal of the secondary we had something that resembles the above photo. If the magnetic shunt material falls out be sure to replace it as it was before. The shunt keeps the core from transferring too much power to the secondary. A magnetic ballast if you will. The shunt acts to control the saturation of the core. A brute force project like this relies on such a shunt for proper operation.

Winding the secondary

Rewinding a MOT with 4AWG is no walk in the park. If you’ve damaged the core insulators, we suggest wrapping a layer of electrical tape in their place. This will help to avoid damaging the insulation on the wire as it is pulled through the core. Our experience is that 3-4 windings is plenty. After all, this spot welder relies on high current and marginal resistance. Not high voltage.

Helical winding

We were careful to ensure that the secondary coil was wrapped in a helical manner to complete the secondary.

Mount the MOT and 2x2 on 2x6 base

We mounted the MOT and 2×2 to the 2×6 base. This particular build used 12″ 2×6 with two 7″ 2×2. These dimensions may or may not work depending on the physical size of your MOT. The only critical part here is keeping the wire length as short as possible.

Attch the upper jaw

After the lower jaw was mounted, we also attached the corner braces. It was found that a spare piece of 2×2 as a shim worked well to align the upper and lower jaw. After the upper jaw was aligned we attached it to the corner braces with screws. This formed the hinged portion of the jaw.

Assemble electrode

The picture above shows the MIG welder tip and the screw type copper lug. This is an improvement from an earlier model we had built. Initially, we used copper tubing with a hole and a piece of 6AWG grounding wire serving as the welding electrode. The grounding wire was held in place by a screw that threaded inside the copper tube perpendicular to the electrode. It was very crude, but it worked. This new method is much more practical.

Assembled electrodes

Here are the two electrodes ready to be fixed to the lower and upper jaws. We double checked the MIG electrodes to make sure they were tight. A loose connection will take heat away from the weld nugget.

Align electrodes with jaws

Evenly aligning the welding electrodes, we were careful to keep the upper jaw in the natural position where it was mounted. This maintained a flat contact area for the welding electrodes. After we were sure that the electrodes had been properly aligned, the jaws were marked. We then drilled a small hole. Since we mounted with the grain of the 2×2 the holes helped to protect from splitting the 2×2.

Attach electrodes to jaws

With the electrodes mounted, we cut the wire to proper length. We never cut the exact amount we need. We always cut more than we need. This rule of thumb should apply to all electrical wiring. After all it is much easier to cut off excess than wrap a new secondary.

Prepare wires for crimp lugs

We bent the wires in to the approximate positions in which they were to be assembled and stripped the wire in preparation for the crimp type welding lugs. It is a good idea to strip more than is needed here as well. Simply cut off excess after sizing up the lugs depth. Never crimp insulation with the lug. This will create a potential problem area due to the loss of conduction.

Wires with crimped lugs

Using a good non insulation crimp tool to secure the wire. We inspected the crimp and gave it the tug test. Simply tug on the wire if it is loose it will pull out. It if doesn’t pull out then an adequate crimp suitable for high current has been made.

Align electrodes

The crimped wires were attached to the welding electrodes with screws. We were careful not to over tighten the screws. If a drywall screw had stripped out of the wood, we would have had to use a larger wood screw in its place. After both welding electrodes were fixed to the jaws, we aligned the electrodes. Using pliers we bent the electrodes so that they contacted each other evenly. The electrodes should be fairly close already since they were aligned before drilling.

Test secondary voltage

We opened the jaws and wired the primary to an electrical cord and then tested the secondary. If the breaker trips, check for the following:

1. The secondary is shorted (the jaws are closed)
2. The magnetic shunts are missing or not properly reinstalled
3. Faulty line wiring to primary or shorted primary
4. Too much load on the circuit of test or undersized breaker

We observed proper electrical wiring practices. It is also stressed that this is a welder and it should have a dedicated circuit as any other welder would have.

Check electrode and material alignment

With the power physically disconnected we verified the welding electrode alignment with the material we intended to work on. Before connecting the power and performing an initial weld, we observed a few safety guidelines. This is a welder and will produce very high temperatures. Keep fingers away from the welding electrodes. Allow the material to cool prior to handling. Always wear eye protection. You may be interested in reading about spot welder parameters. There’s also the problem of combustible materials…

Compaq screen support frame

This Compaq used very thin aluminum to support the screen and connect the hinges. The metal broke and destroyed most of the lower plastic. We were able to make new supports from 22AWG stainless steel sheet metal. All the welds were made using the spot welder with a special power controller. The power controller will be covered in another how-to.

Steady fermentation temperatures, usually at about 65 degrees Fahrenheit, are an important part of brewing beer. Because of this, the wort (unfermented beer) is often temperature controlled during fermentation. [android] needed a temperature controller for fermenting beer in a chest freezer. Much like the energy efficient fridge hack from last month, the chest freezer is switched on and off to achieve the desired temperature. Instead of buying a controller, [android] built around an existing design. His project uses a solid state relay to switch an outlet on and off.

The temperature is controlled by a home thermostat. He removed the thermistor from the unit and extended it with 24 gauge wire so that it can go inside of the chest freezer. Utilizing a junction box, the freezer is plugged into one switched outlet and controlled by the thermostat via the relay. The other outlet is unswitched and provides DC power for the relay using a wall wort transformer. Although this thermostat cannot be set cold enough for lagering, it is perfect for keeping kegs at the correct beer serving temperatures when not being used for fermentation.

[David Cranor] has managed to fit a fully working Uzebox system into an old NES controller. Uzebox, an open source gaming platform based on the ATmega 644 and an AD725 NTSC encoder, is one of a couple systems that are becoming more and more widespread and accessible. There are a number of ready-to-go Uzebox kits available, but for the more hands-on types, [David] has been very generous with his schematics and step by step instructions. These schematics can all be readily reshaped, and would easily fit into controllers with less fun applications and sentimental value.

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With the release of Ubuntu Karmic Koala on 29 October, it is clear that Canonical has aimed its flagship operating system at the enterprise.

When 9.04 shipped, it became apparent that Ubuntu had succeeded where all other versions of Linux have failed — it was an operating system anyone can use. True, there are plenty of good, solid, easy-to-use Linux distributions, but none have offered such a level of simplicity and appeal.

Now, with the release of 9.10, Ubuntu has gone one better and taken its already user-friendly Linux distribution and made a concerted effort to gain ground in the enterprise. Here are 10 reasons why Ubuntu 9.10 should make businesses happy.

1. Software Center
This is the big one. Ubuntu has migrated away from the old add-remove software tool in favour of the Software Center. This tool is just as user-friendly as the old one, but has one feature the old tool lacked — commercial software.

That is correct. Ubuntu has finally included commercial software in its software installation tool. So now users can install not only the usual open-source tools, but they are also able to find plenty of commercial software that can be installed with a few simple clicks — and a purchase here and there.

This feature is good news for business users who need more than the open-source community has to offer.

2. Ubuntu One
If you have ever used DropBox, you know how helpful having a file or folder synchronisation tool can be. Ubuntu One is just as easy to use as DropBox.

It performs instant, automatic synchronisation and offers two plans — a free one with 2GB of space and a paid-for service with 50GB.

You can also add as many machines as you like to your Ubuntu One account.

3. Ubuntu Enterprise Cloud images
With Ubuntu 9.10, businesses can download and use images on the Ubuntu Enterprise Cloud. You can also try out the latest 9.10 server image instantly — on Amazon's Elastic Compute Cloud with a preconfigured Amazon Machine Image. You can even download an image and put it directly into your Ubuntu Enterprise Cloud.

4. Quickly
A new framework called Quickly enables developers to work faster. Quickly provides a command-line framework for generating code projects, storing changes in version control, building packages and releasing software.

To do this, Quickly uses templates that allow specialised behaviours to be defined for different types of projects. The Quickly templates define such behaviours as edit, save, dialog, glade and package. You can think of Quickly as a Rails-like tool for Ubuntu application development.

5. Better Intel graphics support
The new kernel that ships with 9.10 has the kernel mode enabled for Intel graphics. Add to that the driver switch fromthe troubled EXA to the newer UXA acceleration method, and anyone with Intel graphics — and that's a lot of users — will see better performance and quicker resumes from suspend.

6. Faster, stronger AppArmor
Ubuntu 9.10 ships with more profiles for AppArmor and an improved parser that uses cache files, which speed up initialisation at bootup.

Although AppArmor is not a tool for the new Linux user, it lets you set up machines that are even more secure than before. You can even use Firefox with an AppArmor profile. Also included with 9.10 is the ability to move a process to an AppArmor profile or run without one.

7. Blocking module loading
This feature allows the blocking of unloaded modules once the machine has booted. Its primary focus is to prevent kernel root kits from being installed. This measure is handled by one-way sysctl flag /proc/sys/kernel/modules_disabled.

8. Boot time
The elusive 10-second boot time is drawing ever nearer. With the help of many improvements, Ubuntu 9.10 shortens the already short boot time offered by 9.04.

It has not reached 10 seconds yet, but it is close. This improvement will make many business users happy, because boot time is unproductive.

9. HAL deprecation
Some subsystems are being moved away from the hardware abstraction layer (HAL). Most important — to business users, at least — will be suspend-hibernate, which many know has been a big issue for Linux.

By moving these systems from HAL to DeviceKit-Power, DeviceKit-Devices and udev, these systems will be much more reliable. The change should mean that suspend and hibernate will work exactly as expected.

10. Telepathy
Telepathy is new to Linux and serves as a pluggable framework for real-time communication via chat, voice or video over IP, and logging.

Even more exciting, the framework is available to many programs.

Read this
Roundup
Roundup: Ubuntu 9.10

Canonical has released the 'Karmic Koala' update to its version of Linux...

Read more +

Telepathy can share connections between multiple clients, such as messaging, email and collaboration tools.

The stable components of Telepathy are the Gabble Jabber-XMPP connection manager, the Salut link-local XMPP connection manager, the Idle IRC connection manager and the Telepathy-SofiaSIP SIP connection manager. Many other tools are under development.

The primary benefit of Telepathy is that it provides a standard interface to simplify third-party development for applications that communicate with voice or instant messaging functions.

A bright future
If you are like me, you will be excited about the possibilities Ubuntu 9.10 offers on all levels — both personal and enterprise. The Ubuntu experience just keeps getting better and the 9.10 release goes a long way to prove that.

Numerose novità da Amd che ha presentato la nuova piattaforma battezzata Vision, la tecnologia Business Class 2009 per i pc aziendali e la prima cpu quad core dal prezzo inferiore ai cento dollari. Nelle intenzioni di Amd, Vision unisce la potenza di calcolo delle cpu e delle gpu per fornire un'esperienza visiva avanzata agli utenti pc mainstream, ponendo l'accento su come un pc possa essere ottimizzato per applicazioni visive senza limitarsi solo alle caratteristiche tecniche del processore. In pratica, sono stati definiti tre diversi livelli di Vision: Basic, Premium e Ultimate, a cui corrispondono altrettanti livelli di prestazioni, che vanno poi incrociati con le esigenze dell'utente. Anche queste sono state divise in tre fasce: guarda, condividi e crea. La tecnologia Business Class 2009 offre invece all'utenza business i vantaggi degli ultimi modelli di cpu, chipset e hardware grafico di Amd. Infine, nell'ambito della nuova piattaforma per sistemi desktop progettata per i consumatori mainstream, Amd ha presentato il primo processore quad core con un costo inferiore a cento dollari che unisce la potenza delle nuove cpu quad core Amd Athlon II X4 con le capacità del chipset Amd 785G e del processore grafico Ati Radeon Hd 4200. (Fonte: eBiz Italia).

Microsoft late on Friday confirmed that an unpatched vulnerability exists in Windows 7, but downplayed the problem, saying most users would be protected from attack by blocking two ports at the firewall.

In a security advisory, Microsoft acknowledged that a bug in SMB (Server Message Block), a Microsoft-made network file- and print-sharing protocol, could be used by attackers to cripple Windows 7 and Windows Server 2008 R2 machines.

The zero-day vulnerability was first reported by Canadian researcher Laurent Gaffie last Wednesday, when he revealed the bug and posted proof-of-concept attack code to the Full Disclosure security mailing list and his blog. According to Gaffie, exploiting the flaw crashes Windows 7 and Server 2008 R2 systems so thoroughly that the only recourse is to manually power off the computers.

At the time, Microsoft only said it was investigating Gaffie's reports.

Then on Friday, it took the next step and issued the advisory. "Microsoft is aware of public, detailed exploit code that would cause a system to stop functioning or become unreliable," Dave Forstrom, a spokesman for Microsoft security group, said in an e-mail. "The company is not aware of attacks to exploit the reported vulnerability at this time."

Forstrom echoed Gaffie's comments earlier in the week that while an exploit could incapacitate a PC, the vulnerability could not be used by hackers to install malicious code on a Windows 7 system.

Both SMBv1 and its successor, SMBv2, contain the bug. "Windows Vista, Windows Server 2008, Windows XP, Windows Server 2003 and Windows 2000 are not affected," assured Forstrom.

Attacks could be aimed at any browser, not just Internet Explorer (IE), Microsoft warned. After tricking users into visiting a malicious site or a previously-compromised domain, hackers could feed them specially-crafted URIs (uniform resource identifier), and then crash their PCs with malformed SMB packets.

Microsoft said it may patch the problem, but didn't spell out a timetable or commit to an out-of-cycle update before the next regularly-scheduled Patch Tuesday of Dec. 8. Instead, the company suggested users block TCP ports 139 and 445 at the firewall. Doing so, however, would disable browsers as well as a host of critical services, including network file-sharing and IT group policies.

Gaffie's vulnerability was the first zero-day reported and confirmed by Microsoft in Windows 7 since the new operating system went on sale Oct. 22.